1. Field of the Invention
The present invention relates to a thin film magnetic head comprising at least an inductive magnetic transducer for recording, a method of manufacturing the thin film magnetic head, and a magnetic recording apparatus comprising the thin film magnetic head.
2. Description of the Related Art
In recent years, an improvement in performance of a thin film magnetic head which is mounted in a magnetic recording apparatus (for example, a hard disk drive) has been sought in accordance with an increase in the areal density of a magnetic recording medium (such as a hard disk; hereinafter simply referred to as “recording medium”). As recording systems of the thin film magnetic head, for example, a longitudinal recording system in which a signal magnetic field is oriented in an in-plane direction (a longitudinal direction) of a recoding medium and a perpendicular recording system in which a signal magnetic field is oriented in a direction perpendicular to a surface of the recording medium are well known. At present, the longitudinal recording system is widely used, but in consideration of market forces in accordance with an improvement in areal density, it is assumed that the perpendicular recording system instead of the longitudinal recording system holds promise for the future, because the perpendicular recording system can obtain advantages that higher linear recording density can be achieved and that a hard disk on which information has been already recorded has resistance to thermal decay effects.
The perpendicular recording system thin film magnetic head comprises a thin film coil generating a magnetic flux, and a magnetic pole layer emitting the magnetic flux generated in the thin film coil to a recording medium to perform recording. In general, the magnetic pole layer extends from a recording-medium-facing surface (an air bearing surface) which faces the recording medium to the rear, and has a planar shape which includes a uniform width region with a uniform width determining a recording track width of the recording medium and a widening region with a width larger than that of the uniform width region. A position where the width of the magnetic pole layer expands from the uniform width region to the widening region is called “flare point”. In the thin film magnetic head of this kind, when a current flows through the thin film coil, a magnetic flux for recording is generated in the thin film coil. Then, when the magnetic flux is emitted from the magnetic pole layer to the recording medium, the recording medium is magnetized by a magnetic field (a perpendicular magnetic field) for recording generated by the magnetic flux, thereby information is magnetically recorded on the recording medium.
As the structure of the perpendicular recording system thin film magnetic head, some modes have been proposed.
More specifically, for example, a thin film magnetic head in which a facing surface facing a recording medium in a magnetic pole layer has a substantially trapezoidal shape to prevent the effect of side fringing due to a skew is known (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-197613). In the thin film magnetic head, a magnetic pole layer includes two magnetic structures which are separately formed, that is, a main magnetic pole layer which determines a uniform width region and a yoke layer which determines a widening region, and in particular, a rear portion of the main magnetic pole layer is partially covered with the yoke layer.
Moreover, for example, a thin film magnetic head in which a main magnetic pole layer is formed through growing a plating film on a yoke layer, and a front end surface of the yoke layer is inclined or curved to effectively flow a magnetic flux from the yoke layer to the main magnetic pole layer is known (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-197611). In the thin film magnetic head, like the above-described thin film magnetic head, a magnetic pole layer includes the main magnetic pole layer and the yoke layer which are separately formed, and in particular, the main magnetic pole layer is partially overlapped on the yoke layer.
Further, for example, a thin film magnetic head in which a non-magnetic layer is disposed on a main magnetic pole layer to control the thickness and the width of the main magnetic pole layer is known (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-197609). In the thin film magnetic head, like the above-described thin film magnetic head, a magnetic pole layer includes the main magnetic pole layer and a yoke layer which are separately formed, and in particular, the main magnetic pole layer is partially overlapped on the yoke layer.
Further, for example, a thin film magnetic head in which a magnetic pole layer is formed so that the cross sectional area of the magnetic pole layer is gradually reduced toward an air bearing surface, and a front end portion (pole tip) of the magnetic pole layer is disposed closer to a leading side than a plane including a trailing edge of the pole tip in order to improve a magnetic field gradient is known (for example, refer to Japanese Unexamined Patent Application Publication No. 2003-036503). In the thin film magnetic head, the magnetic pole layer is formed so as to include a main pole and the pole tip which are separately formed, and in particular, the pole tip is partially laid on the main pole.
In order to improve reliability of the perpendicular recording system thin film magnetic head and put the thin film magnetic head into widespread use, for example, it is important to establish a manufacturing technique which enables to manufacture a thin film magnetic head with as high performance as possible.
More specifically, firstly, for example, in order to control the recording track width of a recording medium with high precision on the basis of the magnetic pole layer which performs recording, it is required to form the magnetic pole layer as precisely as possible. In this case, in particular, it is important to form a portion corresponding to the uniform width region which substantially determines the recording track width with high precision.
Secondly, for example, in order to stably perform recording in the magnetic pole layer, it is required to increase the amount of the magnetic flux contained in the magnetic pole layer as much as possible. In this case, it is important to sufficiently and smoothly flow the magnetic flux from a portion corresponding to the widening region which contains the magnetic flux to a portion corresponding to the uniform width region which emits the magnetic flux in the magnetic pole layer.
Thirdly, for example, in order to stably maintain information recorded on the recording medium, it is required to prevent the recorded information from being erased without intention due to the magnetic flux contained in the magnetic pole layer to the utmost. In this case, in particular, it is important to reduce the amount of the magnetic flux emitted from a portion of the magnetic pole layer corresponding to the widening region which normally does not emit the magnetic flux without intention.
Although a promising technique of manufacturing a thin film magnetic head on the above-described three points has been in demand, conventional techniques of manufacturing a thin film magnetic head do not sufficiently meet requirements on the three points, so techniques of manufacturing a thin film magnetic head are still susceptible to improvement. Specifically, in consideration of today's technical background in which the areal density of the recording medium is increased at an accelerating rate, it is urgently required to establish a technique of manufacturing a thin film magnetic head which can obtain sufficient advantages on the above-described three points.